Players, former players and administrators have called on clubs and governing bodies to smash open football's "closed shop" and go further to offer opportunities to a more diverse range of people at all levels of the game.

Clarke Carlisle, the Professional Footballers' Association chairman, said there was an urgent need to provide more opportunities for those from all backgrounds who wanted to become referees, coaches, physiotherapists, agents, club officials or take up other professions within the game.

"It's incredibly difficult and about time people acknowledged that it [football] is a closed shop. People try to keep a lid on it but that's the truth," said Carlisle, who was speaking at Kick It Out's Raise your Game conference, at which 39 mentors from across football offered their experience to 200 people hoping to break into the game in a range of roles.

"It's understandable how that has developed because football is so different to any other industry in that experience within the game is vital. But that shouldn't deny anyone else the opportunity of gaining that experience, coming from outside football with an appetite and a hunger to get involved."

Garth Crooks, the former Tottenham Hotspur player turned broadcaster and campaigner, said that the "football family" made it deliberately difficult for outsiders to get involved and more should be done to widen recruitment at the grassroots. "Football is still too much of a closed shop. Coming here is one of the ways of opening the access point. It's still very difficult to become a qualified coach, or a referee or an agent," said Crooks.

"The access points are made deliberately difficult because the game doesn't want the numbers. But the bigger the pool of talent, the better the quality will be. It's about developing the base of the pyramid."

In the wake of protests from players including Rio Ferdinand and Jason Roberts about the game's response to incidents of onfield racism involving Luis Suárez and John Terry, the PFA issued a six-point plan, calling for a domestic version of the "Rooney Rule" in the United States, which guarantees ethnic diversity on shortlists for coaching positions. A Football Association action plan, published in December, pledged to strive for at least 10 percent of referees and level one coaches to come from ethnic minority backgrounds and urged clubs to blow the whistle on racism.

"The industry has to evolve and adapt with the change in attitude," said Carlisle, who plays for Northampton Town and became PFA chairman in 2010. "When you have the difference between what is necessary and the world as it currently is, that's when you get the problems that people complain about. We live in an age now where transparency and accountability is mandatory in every walk of life. It's about time football put glass walls in place rather than glass ceilings."

Among those who acted as mentors for the 200 attendees, largely young people but also including some considering a change of career, were players, former players and managers including Rachel Yankey, Keith Curle and former Arsenal midfielder Paul Davis. Among the 39 mentors, there were also representatives who work on grassroots and community projects, including AFC Wimbledon founder Trevor Hutton, football administrators such as Millwall chief executive Any Ambler, licensed agents, broadcasters, journalists, PRs, referees, physiotherapists and sports psychologists.

It is the third year that Kick It Out, jointly funded by the Premier League, the FA and the PFA, has run the central London conference, which is free to attendees. Kick It Out stays in touch with those who attend in an effort to continue to support them after the event.